Security at the venue estimated up to 1000 people attended what had become the first community memorial service for the Bourke Street attack.

Media were not allowed inside the venue, but it is understood Rabbi Daniel Rabin, president of Rabbinical Council of Victoria, addressed the packed service before Hebrew prayers, which were led by some of Thalia's classmates.

He told those gathered that it was a time for everyone to come together and not only pray for those who died but to pray for a speedy recovery for those who were injured, according to one attendee.

Some left the service in tears, including a young girl who was comforted by her mother.

People have gathered for a memorial service at Beth Rivkah College in East St Kilda. Ten-year-old victim Thalia Hakin attended the school, however, organisers said the service was in honour of all victims of the Bourke Street tragedy.

Jess Mudie, 22, and Matthew Si, 33, were also identified as victims on Sunday.

A 25-year-old man and a three-month-old baby boy were also killed in the tragedy.

Professor David Forbes from Melbourne University's Phoenix Australia Centre for Posttraumatic Mental Health, said witnesses may experience nightmares, intrusive thoughts or memories, and to feel hyper-vigilant in public, for up to two weeks after the incident.

One in five are expected to develop a conditions such as post traumatic stress disorder, depression, an anxiety disorder or substance abuse problems, Professor Forbes warned.

6:51pm on 22 Jan 2017

The Victoria Police restrictive pursuit policy will again come under a microscope after police tailed alleged killer Dimitrios "Jimmy" Gargasoulas for hours before the Bourke Street rampage.

Insurance broking firm Marsh says it was "shocked and saddened" to learn of the death of colleague Jess Mudie.

"Although with us for just under a year, she had already won the admiration and friendship of those she worked with and had a bright future ahead of her," chief executive officer Scott Leney said in a statement.

"Marsh colleagues across Australia join Jess's loved ones and friends in their grief and mourning. We will be providing all the support we can to her family and colleagues at this sad time."

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6:44pm on 22 Jan 2017

The two teenagers who struck out with a baseball bat at the alleged culprit of Friday's rampage through Melbourne CBD say they feel guilty they couldn't stop him.

Tavita Mahina, 17, said "I felt bad cos I thought we could have done more".

He and cousin Isaac Tupou, also 17, told 7 News that Dimitrious Gargasoulas was yelling "F--k the world" and giving 'the finger' to the crowd as he did doughnuts in a car at the corner of Flinders and Swanston Streets.

The cousins had been heading to Alexandra Gardens to play baseball after a church gathering when they heard tyres screeching.

"We just had to take action. No one was doing anything. He looked like he was going to hurt people," Mr Tupou said.

Mr Mahina said: "The car came at us, and then I stepped to the side, and swung the bat, and then he came back and chased us, and was coming to get us and chased us off."

Mr Mahina's father, who didn't give his name, told Seven that move was "very dangerous...I said to him, what about if the guy had a gun? He might [have] shot you."

Victoria Police have released statements and photos on behalf of the relatives of Jess Mudie and Matthew Si, two of the victims of the Bourke Street tragedy.

The family of Ms Mudie, 22, called her their "most badass daughter and sister", praised her devotion to her loved ones, her sense of humour and her headstrong nature.

They quoted Jane Austen's classic novel Pride and Prejudice: "There is a stubbornness about me that can never bear to be frightened at the will of others. My courage always rises at every attempt to intimidate me."

In the statement, Ms Mudie's family said they thanked people for their condolences "but would appreciate this time together to grieve privately".

They said of Jess: "We love your extravagant humour, the fact that you always laughed at your own jokes and your ridiculous names for everything like 'the guch'." the statement said.

"You are always up to do everything and are such bright bubble of joy. Hydration is key, 'Remember me in the morning' is your cocktail of choice, and your personality ensures that will always be the case.

"You are strong, beautiful, determined, always work hard to get what you want and never shy away from a challenge. You always tell it like it is and if someone wanted the truth you would not be afraid to tell them.

"You are so headstrong and assertive in everything that you do, your love for your family and friends is immense, and you are always there when any one needs support."

Matthew Si, 33, a victim of the Bourke Street tragedy.

The statement on behalf of Matthew Si's wife, Melinda, said that Matt, 33, was a devoted husband and a loving father, brother and son.

Matt and Melinda had just finished having lunch together in the city on Friday. They had parted to return to their respective offices when Mr Si was struck down.

"The family would like to thank everyone who helped Matt at the scene and did their best to save him," Mr Si's wife said.

The statement said the family were shattered and requested that their privacy be respected. "She will not be making any further media statements."